Polyglutarimides with improved properties

ABSTRACT

Polyglutarimides exhibit improved optical properties, as well as lowered content of non-aqueous volatiles, when the molten polyglutarimide is mixed with water, methanol, ethanol, or mixtures thereof, and the water, methanol, ethanol, or mixtures thereof is removed prior to isolation and processing of the polyglutarimide.

This is a divisional of U.S. application Ser. No. 638,586, filed Jan. 8,1991, now U.S. Pat. No. 5,126,409.

FIELD OF THE INVENTION

This invention relates to a process for improving the opticalproperties, such as color and transparency, of polymers containing atleast about 30 weight percent of glutarimide units having the ##STR1##wherein R₁ and R₂ are separately H or CH₃, and R₃ is H, C₁ -C₂₀ alkyl,substituted C₁ -C₂₀ alkyl, cycloalkyl, aryl, substituted aryl, aralkyl,substituted aralkyl, or heterocyclic, comprising mixing the polymer inthe molten state with methanol, ethanol, water, or mixtures thereof(hereafter referred to as "the extractant"); removing the extractant;and devolatilizing the molten polymer by application of vacuum. Itfurther relates to the polyglutarimides of improved optical propertiesprepared by this process. It further relates to a process for reducingthe non-aqueous volatile content, especially of residual amines, of thepolyglutarimides, the polyglutarimides of reduced volatile content, andblends of such polyglutarimides with other thermoplastics, such aspoly(vinyl chloride).

BACKGROUND OF THE INVENTION

Polyglutarimides, that is, polymers containing upwards of 10 weightpercent of units of the structure ##STR2## wherein R₁ and R₂ areseparately H or CH₃, and R₃ is H, C₁ -C₂₀ alkyl, substituted C₁ -C₂₀alkyl, aryl, substituted aryl, aralkyl, substituted aralkyl, orheterocyclic, have been known for some years as polymers with uniqueproperties, both in the neat form and in blends. Recently commercialactivity has begun to produce them on a large scale for many uses asplastics in their own right, as modifiers of performance of plasticssuch as poly(vinyl chloride), and as components of binary and ternaryblends. Although improved optical properties are important in certaincombinations with other polymers, such as clear packaging applicationsof blends with poly(vinyl chloride), a high degree of clarity andavoidance of yellowness is most important for the uses ofpolyglutarimides as a clear plastic or a component of multi-layeredcomposites.

All of the polyglutarimides described above, and especially those of theabove structure where R₁, R₂, and R₃ are methyl, exhibit a combinationof high service temperature, high modulus, weatherability, clarity,barrier properties, and an ability to accept impact modification thatoffers commercial opportunities in such fields as automobile components,such as light housing, sun roofs, glazing, and the like, in electronicsuses, such as optical disks and optical fibers, medical devices,business equipment, building/construction, in glazing, as moldingarticles, as monolithic bottles, and in multi-layer composites.

The polyglutarimides are also useful in binary and ternary blends withmany thermoplastics, and as additives for certain thermoplastics,especially poly(vinyl chloride) (PVC). Blends with PVC exhibit animproved service temperature and are useful in siding, equipmenthousing, hot-fill packaging, and the like.

The preferred manufacturing process, which is direct, requires nosolvents, produces a polymer of good thermal stability, can be adaptedto a continuous process, and has advantages over the several othertechniques known to the art, is based on U.S. Pat. No. 4,246,374 ('374),incorporated herein by reference, wherein a polymer with a highconcentration of ester groups, such as from a (meth)acrylate polymer,and especially from a polymer of methyl methacrylate, is contacted withammonia or a primary amine in the molten state in an extruder, and themethanol, primary amine, and by-product secondary and tertiary aminesremoved by vacuum devolatilization.

Other processes for the preparation of polyglutarimides, such astreatment of a methacrylic ester or methacrylic acid polymer in solutionor suspension with a primary amine, may also be utilized to produce apolyglutarimide whose properties may also improved by the extractantprocess of the present invention.

Polyglutarimides prepared by the '374 process or other processes may befurther treated by the method of U.S. Pat. No. 4,727,117 ('117), alsoincorporated herein by reference, wherein the content of acid andanhydride groups in the polyglutarimide are substantially reduced byreaction with an alkylatting or esterifying agent. Particularlyefficient in this respect are alkyl orothoesters, such as tetramethylorthocarbonate, trimethyl orthoformate, dimethyl carbonate, and thelike.

Polymers from both the '374 and '117 technology may occasionally exhibitan undesirable yellow color. Such color may be overcome by toners, whichhowever lower the optical transmission of the processed piece. There hasexisted a need for a process to improve the color and other opticalproperties of the product without doing harm to any of the properties ofthe polyglutarimide, and which could easily and cheaply be applied tothe manufacture of the polyglutarimide of improved color.

Further, polyglutarimides which are useful in food-packagingapplications, such as in monolithic bottles, multi-layer film andbottles, or in blends with PVC for hot-fill applications, need toexhibit a low level of non-aqueous volatiles and of food-simulantextractables. The former refers to volatiles other than water detectedin the polymer prior to or after processing into the final object whichare detected by analysis of the volatiles above the polymer, such as byhead-space analysis of the pellets in a closed container or of thecontents of an empty bottle; in the present context, major contributorsare the mixtures of amines utilized or formed during the imidizationprocess. The latter refers to materials extracted from a formed object,such as a monolithic bottle or a PVC/polyglutarimide bottle, by foodsimulants such as water, ethanol-water mixtures, acetic acid-watermixtures, heptane, and the like.

Further, it is of importance to remove from an additive polymer, such asan additive polymer for PVC, materials which may react with componentsof the PVC or with chemicals used to stabilize and process PVC. Forexample, in certain formulations of PVC containing organometallicstabilizers, the blend of the stabilized PVC with a glutarimide additivewill exhibit poorer heat stability than the same PVC without theglutarimide additive. To overcome the problem, higher levels ofstabilizers may be used, adding to raw material cost, or milderprocessing conditions may be used, adding to processing cost. A means toimprove the thermal stability of glutarimide additives in PVC withoutadditional cost would be desirable.

The art is silent on means to produce very low levels of non-aqueousvolatiles in polyglutarimides, such as poly(N-dimethyldimethylglutarimide), and is silent as to description of such improvedpolyglutarimides themselves. Experience with processing suchpolyglutarimides has led to a desirable target of reduction of volatiles(as measured by trimethylamine analysis) to below 30 ppm, morepreferably to 3 ppm or below, and most preferably to 0 ppm, that is,undetectable by GLC (gas-liquid chromatography) analysis. Levels tobelow 30 ppm can be obtained by slow extrusion (long residence time) andcareful application of vacuum devolatilization, especially by using asecond exposure ("re-pass") of the polyglutarimide, but the process isless economical and can lead to some thermal degradation of thepolyglutarimide.

Further, for processing of additives such as processing aids, impactmodifiers and heat distortion improves, such as polyglutarimides, withPVC, it is desirable to decrease food-simulant extractables so as toachieve acceptable organoleptic properties for materials packaged insuch processed PVC. Further, processing of PVC with such additives,almost always conducted in the presence of one or more thermalstabilizers for PVC, is improved by removal of impurities in theadditives which can effect the thermal stability of the blend. Forpolyglutarimides, it has been discovered, as disclosed in U.S.application Ser. No. 638,585 now abandoned, filled on the same day asthe present invention and with a common assignee, that lowering thevolatile content, as measured by lowering of residual amine, has apositive effect on stability in PVC blends. The volatiles affectingstability may be residual monomethylamine, dimethylamine ortrimethylamine formed as by-products of the imide formation, or othervolatile materials formed during the imidization process. A decreasebelow 30 ppm of such residual amines is desirable to improve thermalstability.

There has thus been sought a practical solution to improving both thefood-simulant and thermal stability aspects of PVC//polyglutarimideblends at little additional expense to the cost of the blend.

SUMMARY OF THE INVENTION

We have found that polyglutarimides of improved color can be formed bymixing the polyglutarimide in molten form with water, methanol, ethanol,or a mixture of these materials, stirring or shearing the mixture tocause intimate mixing, the extractants being in the liquid state, andthen removing the extractants, devolatilizing under vacuum, andisolating the polymer in solid form. The polymer so formed, whencompared to unextracted polyglutarimides of otherwise similar processinghistory, also has a reduced level of non-aqueous volatile components,will have equivalent or superior performance in the response toextraction with food-simulants, and is more thermally stable in PVCblends.

DETAILED DESCRIPTION OF THE INVENTION

The polyglutarimide to be mixed with the extractant is defined as apolymer having at least 30 weight-percent of units with thedimethylglutarimide cyclic structure noted above. Preferred is thatstructure where R₁ and R₂ are both methyl groups and where R₃ ishydrogen, lower (C₁ to C₄ alkyl), or cyclohexyl. Especially preferred isthe structure where R₃ is methyl, as that unit,N-methyldimethylglutarimide, yields glutarimides of a commerciallydesirable balance of high service temperature, good barrier properties,weathering, and the like.

Other units may be present in the polyglutarimide structure, such asthose derived from esters of (meth)acrylic acid, or from vinyl aromaticmonomers such as styrene and the like; lists of such copolymerizablemonomers are found in the incorporated references. Especially preferredare units derived from methyl methacrylate. Units derived from(meth)acrylic and acid and/or (meth)acrylic anhydride, which are formedduring the imidization process, may be present in the polymer to beextracted. For certain uses, such as a modifier for PVC, it is preferredthese functionalities be removed prior to extraction, by methods such astaught in '117.

The molecular weight of the polyglutarimide is not critical to theextraction process, although it is preferred for most end uses of thepolyglutarimide that the molecular weight be between about 50,000 and250,000 (weight-average).

The mixing of the polymer with the extractant in the molten state (whichis also referred to as "washing" of the polymer melt with theextractant) may be accomplished in any of a variety of processingdevices, such as autoclaves, wiped film stills, and the like, but anextruder, especially a devolatilizing extruder, is preferred. Use ofother diluents or solvents are not necessary and add to the cost ofprocessing; indeed, the use of toluene as a diluent/wash was ineffectivein reducing color.

The extruder may be a single-screw or twin-screw device of variousconfigurations, and may be equipped with mixing devices, such as bafflesor static mixers, to assure better mixing. The temperature of mixing ispreferably between 200° and 400° C., and especially preferred is from260° to 300° C. The temperature of the extractant may be from about roomtemperature to about 205° C.; it is preferred to introduce theextractant with a pressure pump at temperatures about 205° C. formethanol or ethanol, and at about room temperature for water.

Mixing times may be from less than 1 second to above 1 minute, dependingon the size of the washing or mixing zone, and the rate at which theimide is passed through the extruder. Pressures developed will normallyrange from about 3400 to about 5500 kPa, but wider ranges can beemployed.

It should be stressed that the present invention differs from processesknown to the art where vapors of low-boiling liquids, such as water, areintroduced near or at vents for vacuum devolatilization to aid inremoval of low-molecular weight volatiles for molten polymers, such aspolyolefins. Although any residual water or alcohol removed at thedevolatilization zone will aid in removal of other volatiles, such asamines, the water or alcohol added in the mixing step aids in colorimprovement by removal of colored or color-forming impurities in aliquid wash step.

The invention encompasses several means of processing to obtain thepolyglutarimide prior to mixing with the extractant. The polyglutarimidemay be prepared separately by any of many methods known to theliterature, such as in solution or in a heterogeneous mixture withaqueous amine, isolated, and cooled; the separate preparation mayoptionally include an acid/anhydride removal process, and willpreferably involve a devolatilization step. The cooled polymer is thenheated from the solid state to the molten state prior to mixing with themethanol, ethanol, water, or mixtures thereof.

A preferred process to minimize thermal contact will cause theglutarimide units to be formed in the molten polymer immediately priorto the mixing with the methanol, ethanol, water, or mixtures thereof.The imidized polymer can be formed by any of several known methods,taken into the molten step for removal of reactants, and then mixed withthe extractant. Preferably the imidization is conducted in one zone of areactor and the polymer then passed into an adjoining zone for mixingwith the extractant. Even more preferred is the method where theimidization polymer is devolatilized to remove solvent, reactants,by-products, and the like, and then immediately mixed with theextractant. Removal of much of the amine content lowers the possibilityfor catalysis of hydrolysis of the ester or anhydride groups tointroduce a higher acid content.

As noted, many uses of the polyglutarimides require removal of the acidand anhydride groups present prior to processing into useful objects orcombination into blends. The process of '117 is most useful in thisrespect. It is preferred that the polyglutarimide be formed in one zoneof the extruder, passed to a separate zone for addition of theacid-reductant agent, and then mixed with the extractant in a thirdzone. It is especially preferred to conduct a vacuum devolatilization onthe acid-reduced polyglutarimide after the acid-reduction step but priorto the mixing with the extractant.

When the residual amine content is lowered to below about 100 ppm,preferably below 50 ppm, the polymer may be mixed with a low level of areducing agent further to improve the color. Preferred ishypophosphorous acid at from about 0.05 to about 2 weight percent (basedon the total extrant used) wherein an improvement in color is seen overa similar polymer processed in a similar manner but without thehypophosphorous acid. If the hypophosphorous acid is added when theamine content is greatly above about 100 ppm, corrosion of the metal mayoccur to cause haze in the isolated polymer. It is preferred to add thehypophosphorous acid in the wash step, admixed with the methanol,ethanol, water, or mixtures thereof. Levels higher than 2% ofhypophosphorous acid may be used, but will add to the cost.

The extractant procedure may also be used as a means for delivery ofother additives, which normally are admixed into the melt aftercompletion of all washing and devolatilization steps. For example, if itis desired to introduce a phosphite stabilize, such as tris(nonylphenyl)phosphite, into the glutarimide polymer, the phosphite may be dissolvedor suspended in the extractant and mixed with the polyglutarimide. Byadding stabilizer in this means, protection against thermal instabilityis introduced to the polyglutarimide during a period where the moltenpolymer is exposed to heat.

The extractant is separated and removed through a vent near the die endof the extruder. The liquids may be recovered, distilled or otherwisepurified, and re-used in the extractant step. The extractant may beremoved as a liquid, or may be distilled from the reactor and condensed.

The extracted polyglutarimide while still in the molten state and afterremoval of the extractant is exposed to a last vacuum devolatilizationto remove the final traces of water, ethanol, or methanol and any lastvolatile materials not removed with the extractant. Thisdevolatilization is conducted under a vacuum of at least 580 mm. ofmercury, at a vent located between the washing zone and the additiveport.

The polyglutarimide may then be compounded while still in the moltenform with stabilizers, pigments, ultraviolet stabilizers, dyes, fillers,impact modifiers, and the like prior to extrusion into pellets or ashaped object; for some uses, the polymer may be extruded directlywithout any further additives.

For most efficient removal of residual amines, the extruder may beconfigured so as to have two or more vacuum devolatilization zones, oneprior to the extractant wash step, and one following the removal of theextractant. It is desirable to monitor the volatiles from the collectedpolymer and adjust the devolatilization conditions to achieve anon-aqueous volatiles analysis (or analysis for content of a majorvolatile component, such as trimethylamine) below 30 ppm, moreespecially below 3 ppm, and most especially at 0 ppm.

The polyglutarimide may be re-converted to the molten state from solidform, such as pellets, sheet, or re-grind, or the extractant step may becarried out at the end of the processing extruder used to prepare thepolyglutarimide or to carry out the acid-reducing reaction.

The polyglutarimide of reduced color may be directly processed intouseful articles; however, it is more common to isolate the extractedpolyglutarimide as strands which are chopped into pellets. These pelletsmay be then used for many purposes in blends, formation of sheet, film,or molded objects.

After extraction is completed, the molten polymer may be treated withconventional additives, such as dyes, pigments, UV absorbers, thermalstabilizers, and the like. Especially useful in this respect for use inweatherable clear applications are ultraviolet stabilizers such ashindered amine light stabilizers (HALS), benzotriazoles, and the like.Improved color on processing of benzotriazole-stabilizedpolyglutarimides with sharply reduced levels of residual amines is oftenobserved. It may be also blended with other polymers directly, and/orcombined with fibers, such as glass or carbon fibers, or fillers priorto isolation as pellets.

The advantages of the polymer of lower yellowness index and otherimproved optical properties will be seen in such uses as optical fibers,lenses, glazing, lighting fixtures, monolithic bottles, multi-layeredbottles with layers of other clear plastics such as polyester orpolycarbonate, and the like.

The polyglutarimide may be blended with PVC homo- or copolymers as fullydescribed in U.S. Pat. Nos. 4,255,322, 4,650,824, and 4,727,117, allincorporated by reference. It is preferred for best compatibility withPVC that the blend be a blend of from about 5 to about 95 parts ofpoly(vinyl chloride) with from about 5 to about 95 parts, preferablyfrom about 5 to about 30 weight percent of glutarimide units having thestructure ##STR3## wherein R₁ and R₂ are separately H or CH₃, and R₃ isH, C₁ -C₄ alkyl or cyclohexyl. It is more preferred that the blend bewith a polymer wherein R₁, R₂, and R₃ are CH₃, and prepared by theprocess described above where the acid/anhydride content is reduced. Itis further preferred that the acid-reduced polyglutarimide bedevolatilized prior to mixing with the extractant.

PVC, usually as a homopolymer of vinyl chloride, but also as a copolymerwith, e.g., vinylidene chloride, ethylene, vinyl acetate, and the like,or as a graft copolymer of vinyl chloride onto a pre-formed rubberypolymer, such as a polyolefin or a poly(acrylate), may be blended withthe extracted polyglutarimide at use levels preferably of about 5 toabout 30 parts of polyglutarimide per 100 parts of PVC resin, althoughboth higher or lower amounts may be useful to fulfill certain propertyrequirements. The blends may contain any of several well-knownstabilizers for PVC, such as organotin stabilizers, calcium-zincstabilizers, organolead stabilizers, barium-cadmium stabilizers, and thelike.

The improved thermal stability of the glutarimide of the present processin PVC and the lowered non-aqueous volatiles content and food-simulantextractants can be utilized in the manufacture of PVC bottles andcontainers, especially for hot-fill, such as for ketchup, jellies,syrups, and the like; in siding for buildings, window profiles, and thelike; in housings for electrical components; and in many other usesrequiring the flame resistance and toughness of PVC and the added heatdistortion resistance imparted by the polyglutarimide.

EXAMPLES Examples 1-5

These examples illustrate the improvement in optical properties obtainedwhen a glutarimide polymer is prepared and directly mixed with water ormethanol.

A polymer containing predominantly (ca. 76 weight %)N-methyldimethylglutarimide units having a nitrogen content of 6.0%, aglass temperature of ca. 150° C., and with a total of ca. 5% acid andanhydride groups, was prepared in a 50.8 mm. Welding Engineerstwin-screw extruder equipped with zones for admixture of methylamine andfor devolatilization of excess amine and reaction by-products. Thepoly(methyl methacrylate) feed was supplied at 70 grams/minute, andmonomethylamine was fed at a rate of 38 cc/minute at 5.51 mPa pressureat 280°-300° C.

The imidized polymer melt was then passed into a zone equipped with ameans for pumping in (and for removing) the water or methanolextractant. The extractant was supplied from a source at roomtemperature at a rate of 14 cc./minute. A pressure of ca. 3.8 mPa wasobtained. Mixing with the extractant was conducted in the reaction zonenormally used for contact with the acid/anhydride reductant, where thatprocess variant is applied. The polymer was then led through adevolatilization zone, into a die, and stranded and chopped intopellets.

The pellets were molded into test bars for determination of opticalproperties by test method ASTM D-1925. All data are the mean of fiveoptical determinations.

    ______________________________________                                        Example   Extractant        TWLT    YI                                        ______________________________________                                        1         none (control)    90.47   3.39                                      2         Methanol          90.59   3.02                                      3         Methanol:water (1:1)                                                                            90.74   3.02                                      4         Water             90.81   2.16                                      5         Methanol          91.12   1.63                                      ______________________________________                                         TWLT: total white light transmission; YI: yellowness index.              

Examples 6-12

This example illustrates the positive effects of water or methanolextracting or washing on an imide sample which has been re-worked. Apolymer similar to that described in Examples 1-5 was imidized,devolatilized and extruded, but no extractant was applied. The pelletswere then re-fed to the extruder under similar conditions (50grams/minute) except that no amine was added to the imidization reactionzone, and then extracted with water or methanol fed at a rate of 11cc/minute at a pressure of 3.65 mPa. The extracted material wasdevolatilized, pelletized and molded. Mixing with the extractant wasconducted in the reaction zone normally used for contact with theacid/anhydride reductant, where that process variant is applied.

    ______________________________________                                        Example                                                                              Extractant      TWLT    YI                                             ______________________________________                                        6      none (control)  90.0    5.8                                            7      Methanol        90.1    5.2                                            8      none (control)  89.7    6.1                                            9      Methanol:water (1:1)                                                                          90.6    3.9                                            10     none (control)  89.9    5.8                                            11     Water           90.6    3.1                                            12     none (control)  89.8    6.3 (re-measured                                                                  next day)                                  ______________________________________                                    

Examples 13-15

These examples illustrate the improvement in optical properties in apolyglutarimide which has been treated previously to reduce the contentof acid and anhydride groups in the polymer.

A polymer of MW ca. 110,000 and imide nitrogen content 4.79%,corresponding to ca. 45% imide content, was prepared with no extractingstep and with no additives. The acid and anhydride content were reducedto low levels by contact with dimethyl carbonate. It was thenre-processed in a 5.1 cm. extruder equipped with means for washing,venting, and a final devolatilization. In the re-processing step, thepolymer was fed at a rate of 59 kg./hour, the melt was at a246° C.,methanol was fed at 4.6 kg./hour, and water at 7.3 kg./hour. The firstzone of the extruder, normally used for imidization was capped; thesecond zone, normally used for acid-reduction, was at 260° C. and 1.7mPa pressure.

Samples were analyzed for color and residual TMA content. The valuesgiven are the average for separate determinations of several portions ofre-processed polyglutarimide. The extractant process lowers thetrimethylamine content to where no peak is seen on the GLC analysis. Asit is preferred to avoid two separate heating steps, the extractingprocess may be applied to a similar polymer directly (i.e., withoutcooling and isolating) after it is imidized, acid-reduced, anddevolatilized.

    ______________________________________                                        Example                                                                              Treatment    TMA     MeOH  TWLT   YI                                   ______________________________________                                        13     None (control;                                                                             9       39    90.4   2.4                                         double-passed)                                                         14     Methanol     0       26    90.5   2.0                                  15     Water        0        3    90.8   1.75                                 ______________________________________                                    

Example 16

This example demonstrates the improved thermal stability in PVC when thewater-extracted polymer of Example 15 is compared with a similar polymerwhich was not water-extracted (and also did not have an additional heathistory of melting and cooling).

The polymer and the control are ground to a powder, and admixed with PVCand other additives in a "masterbatch" formulation. Three differenttypes of stabilizers were studied. Evaluation is performed by heatingthe masterbatch plus polyglutarimide on a two-roll mill, the front rolloperating at 26 rpm and the rear at 20 rpm, at 205° C. After fusionoccurs, samples are removed every three minutes and cut or pressed into25.4 by 3.15 mm. pieces, which are then ranked for color. The time toblack for an "unmodified control" with no glutarimide polymer is noted,and the time to black for the various extracted polymers. Although thewater-extracted glutarimide polymer is less stable than the "unmodifiedcontrol," it exhibits a significant advantage in stability over thesample which was not water-extracted. The extractant treatment is lessreproducible in calcium-zinc formulations, or in tin formulations basedon K=50 PVC, although in most experiments an improvement in heatstability is seen for the extracted polyglutarimide.

    ______________________________________                                        Polymer       Example 2 Control (not re-extruded)                             ______________________________________                                        trimethylamine, ppm                                                                         0         56                                                    methanol, ppm 0         70                                                    dimethyl carbonate, ppm                                                                     --        300,200                                               ______________________________________                                    

Tin stabilized formulation:

    ______________________________________                                                        PHR (parts per                                                                hundred resin)                                                ______________________________________                                        PVC, K 60         100                                                         Glutarimide       25                                                          polymer                                                                       Octyl tin stabilizer                                                                            1.5                                                         Glycerol monostearate                                                                           0.6                                                         Waxes             0.3                                                         Acrylic processing aid                                                                          1.0                                                         MBS impact modifier                                                                             8                                                           Time to char, min.                                                            no glutarimide    15                                                          Unextracted       12                                                          Example 15        15                                                          ______________________________________                                    

Lead stabilized formulation:

    ______________________________________                                                         PHR                                                          ______________________________________                                        PVC, K 50          100                                                        Glutarimide        25                                                         polymer                                                                       Lead stearate stabilizer                                                                         4.7                                                        Lubricants         0.8                                                        Acrylic processing aid                                                                           1.5                                                        Titanium dioxide   4                                                          Acrylic impact modifier                                                                          10                                                         Time to char, min.                                                            no glutarimide     54                                                         Unextracted        36                                                         Example 15         51                                                         ______________________________________                                    

Example 17

If the process described in Example 5 is repeated with methanol replacedby ethanol, similar results will be obtained as pertains to thermalstability and reduction of volatiles.

Examples 18-20

This example illustrates the effect of hypophosphorous acid in improvingcolor. In a separate experiment similar to that of Examples 6-12, thepoly(glutarimide) was treated with no extractant, with methanol, andwith methanol containing 1% hypophosphous acid. The yellowness indexvalues were:

    ______________________________________                                                             YI                                                       ______________________________________                                        Example 18 (re-passed, no extractant)                                                                7.79                                                   Example 19 (methanol)  6.84                                                   Example 20 (methanol, 1% H.sub.3 PO.sub.2)                                                           3.35                                                   ______________________________________                                    

We claim:
 1. A polymer having a trimethylamine content of below 30 ppmand containing at least about 30 weight percent of glutarimide unitshaving the structure ##STR4## wherein R₁ and R₂ are separately H or CH₃,and R₃ is H, C₁ -C₂₀ alkyl, substituted C₁ -C₂₀ alkyl, cycloalkyl, aryl,substituted aryl, aralkyl, substituted aralkyl, or heterocyclic,prepared by the process comprising:a) mixing the polymer in the moltenstate with methanol, ethanol, water, or mixtures thereof in their liquidstate; b) removing the methanol, ethanol, water, or mixtures thereof intheir liquid state; and c) devolatilizing the molten polymer byapplication of vacuum.
 2. The polymer of claim 1 wherein R₁, R₂, and R₃are CH₃, and wherein the polymer further contains units derived frommethyl methacrylate.
 3. The polymer of claim 1 having a trimethylaminecontent of less than about 3 ppm.
 4. A blend of from about 5 to about 95parts of the polymer of claim 1 with about 95 to about 5 parts ofpoly(vinyl chloride).
 5. The blend of claim 4 containing from about 1 toabout 40 parts (per 100 parts of the poly(vinyl chloride)) of thepolymer containing at least about 30 weight percent of glutarimideunits.
 6. The blend of claim 5, wherein the polymer has a content oftrimethylamine less than about 3 ppm.